Soft image

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GregD

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Greg
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I brought a Sigma 18-50 f2.8-4. and I took it out for a spin today not sure about the images was shooting hand held with OS on and some seem a little soft not out of focus just soft was not shooting at edges all the time shots at 32mm f11 still not great though it could be poor conditions and poor photographer ;).

I was told when I got this to check the quality because of Sigmas strict QC or lack of, how can i check to see if it is the lens or the person behind the lens?

Any advice would greatly be received also if it is the lens am I best trying to send it back to the place o got it from or Sigma it is a week old.

Thanks

Greg
 
Any chance of a pic so we might be able to judge ?

Put it on a tripod with OS off and take some pics with a cable release or timer
and if still soft send it back for inspection.If bought online ring Sigma first,if a shop,take it back to them.
 
Interesting :thinking: I shall be watching this post carefully as I have been having problems with my Sigma 120 - 400 too :cuckoo:
 
right looking at this with a fresh set of eyes not as bad as I first thought might be a focusing issue, or a Do not take photos when hungover issue!!!

but I am still not 100% links to original pics none edited just converted to jpeg

http://i552.photobucket.com/albums/jj355/GregD450/IMG_3677.jpg

http://i552.photobucket.com/albums/jj355/GregD450/IMG_3670.jpg

http://i552.photobucket.com/albums/jj355/GregD450/IMG_3662.jpg

http://i552.photobucket.com/albums/jj355/GregD450/IMG_3658-2.jpg

http://i552.photobucket.com/albums/jj355/GregD450/IMG_3651.jpg
 
3651- you missed the focus, where the child is about 6 inches in front of the plane of focus. Probably user error either that or its SERIOUS back focus!!! :lol:

3658 - looks okay to me, probably just a case of adding a bit of USM, but it looks fine to me. :)

3662 - Looks like the focus has been missed again, this time front focus judging by the wall on the left. I doubt the AF system could've even locked onto anything on the same plane of focus as the wall - did you focus lock? Otherwise that might be front-focus. :|

3670 - slow shutter speed wouldn't have helped the sharpness, does look a bit soft but again probably just needs a bit of USM. :shrug:

Overall, a bit of unsharp mask would help the shots, watch your shutter speed. Some shots are okay, others are probably down to you missing the focus, others possibly the camera's fault.

Pop it on a tripod and and take some test shots at around f/4 focus on a ruler. Centre AF point. Mirror Lock-up. Try the different focal lenghts. Check they look sharp. If it's well focussed and sharp, then its the users error. If not the lens may be soft or front/back focussing or perhaps both or even all three :bonk:
 
thanks will try that appreciate the advice i will give that a try now.

just out of interest what is front and back focus?

hope thats not too much on a noob question
 
Essentially front focus is the focus plane being either slightly further forward than the intended target or vice versa for back focus.

It's just the tolerances cameras and lenses are made to, some pairs are calibrated better to each other than others. Many claim Sigma's tolerances are wider than Canons hence the potential for focussing issues. Because all cameras and lenses may front/back focus slightly you may notice the issue when using certain camera/lens combos and it could be perfect on another camera or another lens.
 
Suspect focus and depth of field issues. DoF is shallow at f/2.8.
 
Where were hou focusing?
What focus point?
Was camera on a tripod?
Were you using Miror Lockup?
What aperture/Shutter speed/ISO?
 
GregD said:
ok as suggested I have done this looks alright to me not sure if I have done this right though anything I should have done differently

http://2.bp.blogspot.com/_GzibJwLubCs/S7jXlt1hN-I/AAAAAAAAAME/Q90y3Xy2aYw/s1600/test_0009.jpg

http://1.bp.blogspot.com/_GzibJwLubCs/S7jXl3rXovI/AAAAAAAAAMM/iX0MiWRqM2Y/s1600/test_0010.jpg

http://1.bp.blogspot.com/_GzibJwLubCs/S7jXl3rXovI/AAAAAAAAAMM/iX0MiWRqM2Y/s1600/test_0011.jpg
Click to expand...

It would help to know where you actually focussed. The 3 is sharp - but did you focus there?
 
How are you focusing? This may have a tremendous impact. I recommend using the centre AF point only, then recompose and then execute. Works to me 100% for static objects. You can decouple focusing and shutter via custom fx.

The baby is clearly backfocused but the cannon front focused. Some lenses don't like using all focus points, or worse in a random way. Cameras are NOT intelligent and do not know what your actual subject is.

The other 2 were city scenes. f/14-18 is a perfect recipe for soft images due to diffraction. f/8-11 is as high as you should go unless you have a special reason (need a slower speed at ISO100 or extra large DOF).
 
GregD said:
but I am still not 100% links to original pics none edited just converted to jpeg
Click to expand...

Did you sharpen the raws before converting to jpeg?
If not, you need to.
If you don't know how to then just stick with jpeg from the camera and bump the in-camera sharpening up a notch from the default.
RAW needs to be sharpened to get the best out of it.
 
User Name said:
Did you sharpen the raws before converting to jpeg?
If not, you need to.
If you don't know how to then just stick with jpeg from the camera and bump the in-camera sharpening up a notch from the default.
RAW needs to be sharpened to get the best out of it.
Click to expand...

What he said.

Also, according to our member Desantnik, Canon cameras have an antialiasing filter which actually softens image slightly and Canon themselves reccommend sharpening with the USM in photoshop. Any sharpening will do though, 3 notches of sharpening in Canon DPP usually works a treat for me.
 
Pretty much every DSLR will have an Anti aliasing filter. There is a website showing the results of removing the filter on a Nikon. Without the filter the images are sharper straight from the camera, but you'll get aliasing (jagged edges) on straight lines.

See here for an example of removing the AA filter:

http://maxmax.com/nikon_d200hr.htm

edit: this is the one I was thinking of:
http://www.maxmax.com/hot_rod_visible.htm
check out "Area 3 Notice the Moiré pattern on the air conditioner grates".

The AA filter adds blur, that's why RAWs need to be sharpened.
 
the original raws I did shaprpen I just put unedit versions on here so you could see them before editing,

the photos of the tape were from a tripod mirror lock up and focused on the 4 using the center AF.

I have heard about the decoupling of the AF and the shutter how is this done.

Think what I will take away from this is I still have a long way to go but practice makes perfect.
 
Thank you for all the advice on here, have changed AF to the * and am loving that makes a lot of difference I also noticed something else very very silly I did which was have AI Servo on so when I recomposed think it was ajusting focus.

Had another play with the lens today and am pleased with the purchase think I was just having a panic I had brought something that was no better that the 18-55 IS kit lens.

Now just to keep practicing, anyone know anywhere in Cumbria around the lakes that does any courses would like to get together with a group to help develop.
 
There are a few courses in North West Cumbria, but Cumbria is a big area - you could be miles away lol
 
I am from Carlisle area, but am willing to travel to help me develop spend a lot of time in workington and whithaven and around the lakes. joys of covering all of cumbria with IT Support.
 
GregD said:
I am from Carlisle area, but am willing to travel to help me develop spend a lot of time in workington and whithaven and around the lakes. joys of covering all of cumbria with IT Support.
Click to expand...

Cool, the courses that were being run were in Whitehaven. I'll get some details for you!
 
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